Missouri imposed new speed limits on its highways in time for the January 1958 publication of this map. These limits stayed in effect until the federal adoption of a national maximum speed limit of 55 miles an hour in 1974. Current speed limits in Missouri are different and depend much more on conditions of the individual roadway rather than the classification of the highway.

Also note the separate daytime and nighttime speed limits.

U.S. highways are incorrectly referred to as "federal highways".